Techniques for continuous brush plating utilizing a porous brush member made of a hydrophobic material are described and claimed in my U.S. Pat. No. 4,452,684 issued June 5, 1984. In that patent, high speed plating of parts is accomplished by passing the parts lengthwise of a stationary brush member with the parts in contact with the surface of that member. According to that patent, the brush member is formed of a hydrophobic material having interconnected pores. A distribution conduit located centrally of the brush member is used for distributing plating solution outwardly through the pores to maintain a continuous supply of fresh solution on its periphery. The brush member disclosed in that patent preferably is covered with a screen-like material serving as an anode and has a soft porous outer covering along which the parts to be plated are "brushed." Preferably the stationary brush member has at least one planar surface, a sharply radiused surface and one relatively large radiused surface extended lengthwise thereof, each of which may be positioned along the path of the parts, for the purpose of plating parts of different shapes. Rapid, selective plating of small portions of metal parts is a achieved because a constantly replenished supply of plating solution is present on the brush surface and is available for the plating of a selected surface of a part.
Rotatable cylindrical brush members arranged so that the surface of an absorbent brush is dipped into a bath of an electrolytic plating solution, or in which the solution is somehow poured onto the surface, are known in the art. Uniformity of amount of metal plated on the part is difficult to achieve with such arrangements, at least in part because of the difficulty of maintaining a uniform and continuous supply of metallic ions on the surface of the brush member. The rate of plating is relatively low, due in large part to ion depletion in the plating solution.
Both the approach in my prior U.S. Pat. No. 4,452,684 and the rotary brush approach as described for example in U.S. Pat. No. 4,361,470 have important advantages. High production rates and a precisely controlled application of plating material are among the objects and advantages obtained with the brush disclosed in U.S. Pat. No. 4,452,684. However, for many uses, rotary brushes have important advantages. When an elongated part is passed lengthwise of a rotating cylindrical brush in tangential contact with its periphery, rotary brush plating techniques inherently produce a grain structure of the plating material on the part which runs substantially lengthwise of the part. For parts serving as connectors, this lengthwise grain structure, which extends parallel to the direction of insertion and removal of the plated connector, results in a reduction of the wear of the plated material from the part.